title: [Investigation of free volume changes in the structure of the polymer bifocal contact lenses by means of the positron annihilation method].
abstract: Positron annihilation lifetime spectroscopy has been applied of free volume properties in bifocal contact lenses. The measurements have been made on new lenses and then after one, and two weeks wearing by the patient. The longest lifetime, obtained via three-component analyses of the spectra, was associated with the pick-off annihilation of ortho-positronium trapped in the free volume. After one, and two weeks wearing of the lenses changes in the ortho-positronium lifetimes and the relative intensity of the longest component were observed. These results are discussed on the basis of a free volume model.
authors.affiliation: Instytut Fizyki, Zakład Badań Strukturalnych i Fizyki Medycznej, Akademia im. Jana Długosza w Czestochowie. j.filipecki@ajd.czest.pl
authors.forename: Jacek
authors.initials: J
authors.lastname: Filipecki
authors.forename: Piotr
authors.initials: P
authors.lastname: Korzekwa
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Filipecka
authors.forename: Manol
authors.initials: M
authors.lastname: Dorobanow
authors.forename: Dominika
authors.initials: D
authors.lastname: Korzekwa
authors.forename: Witold
authors.initials: W
authors.lastname: Korzekwa
authors.forename: Małgorzata
authors.initials: M
authors.lastname: Hyla
mesh_terms: D003261:Contact Lenses; D006801:Humans; D008422:Materials Testing; D008956:Models, Chemical; D011108:Polymers / Q000737:chemistry*
chemical_list: D011108:Polymers